(1) Field of the Invention
The present invention relates to a digital-to-analog (D/A) converter connected at a poststage of a digital signal processing circuit in a digital audio appliance.
(2) Description of the Prior Art
Generally speaking, in such a sort of digital-to-analog converter (will be referred to a "D/A converter"), it is so arranged that a digital signal value outputted at each sampling point of a digital signal processing circuit is converted into an analog signal value (analog stepped wave) by way of a ladder type D/A convertering circuit, and then the resultant analog signal value is filtered by an LPF (low-pass filter to remove a high frequency signal component therefrom.
Then, the load given to the LPF is reduced by employing such a technique as over sampling operation, so that deterioration of audient sound (tone) quality caused by the LPF may be mitigated.
However, since the output signal wave of the above-described conventional D/A converter has a shape of a stepped waveform, the low-pass filter (LPF) is necessarily required. Accordingly, the phase characteristic is deteriorated and the lengthy delay time occurs due to an employment of such an LPF. It is therefore difficult to improve the audient sound quality at a satisfactory level.